Most of electronic devices, such as mobile phones or personal digital assistants (PDAs), commonly include buttons for functional controlling, such as, power switch button, volume controlling button, screen locking button, or camera switch button. In addition, the buttons are generally combined with light sources, such as light emitting diodes, to improve attractiveness. However, the light sources are generally located below the buttons, due to different distances between the light sources and a surface of the button and an uneven reflection, light transported to the surface of the button is uneven, which leads to a bad effect.